Surface tension of water at 1.2 atmospheric pressure

Options

A. More than 74 dynes/cm
B. Less than 74 dynes/cm
C. Same 74 dynes/cm
D. Can not say

Answer

To solve the question regarding the surface tension of water at 1.2 atmospheric pressure, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Surface Tension**:
- Surface tension (T) is the force per unit length acting along the surface of a liquid, which causes the surface to behave like a stretched elastic membrane.

2. **Identify the Given Information**:
- The pressure given is 1.2 atmospheric pressure (atm).

3. **Recall the Formula for Excess Pressure in a Bubble**:
- The excess pressure (ΔP) inside a soap bubble is given by the formula:
\[ \Delta P = \frac{4T}{r} \]
- Here, \(T\) is the surface tension and \(r\) is the radius of the bubble.

4. **Relate the Given Pressure to Surface Tension**:
- In this case, the excess pressure inside the bubble is equal to the atmospheric pressure. Therefore:
\[ \Delta P = P_{\text{atm}} = 1.2 \, \text{atm} \]

5. **Convert Atmospheric Pressure to SI Units**:
- To use this in calculations, we need to convert atmospheric pressure to pascals (Pa):
\[ 1 \, \text{atm} = 101325 \, \text{Pa} \]
- Thus,
\[ P_{\text{atm}} = 1.2 \times 101325 \, \text{Pa} = 121590 \, \text{Pa} \]

6. **Substitute into the Formula**:
- Now substituting the values into the formula for excess pressure:
\[ 121590 = \frac{4T}{r} \]

7. **Rearrange to Find Surface Tension**:
- Rearranging the equation to solve for surface tension \(T\):
\[ T = \frac{121590 \cdot r}{4} \]

8. **Conclusion**:
- Since the radius \(r\) of the bubble is not provided in the question, we cannot calculate a specific numerical value for the surface tension. Therefore, the answer is:
- **Cannot determine the exact value of surface tension without knowing the radius.**